Mintu Turakhia, MD, MAS, a cardiac electrophysiologist at the hospital and instructor at the Stanford University School of Medicine, was one of the first physicians to treat Sassoubre after she was transferred from the emergency department to the cardiovascular intensive care unit. An electrocardiogram revealed that she was suffering from ventricular tachycardia, a type of abnormally fast heart rate.
"Approximately 95 percent of people who have the ECG pattern that Ms. Sassoubre had would be considered to have a structurally normal heart, not ARVC," Turakhia said.
Nevertheless, he suspected that she was the rare exception. For one, he said he did not think this type of arrhythmia could sustain itself, uninterrupted, for as long as it did in her case.
Turakhia and his team performed a series of non-invasive heart tests to help make a diagnosis, but the results were inconclusive. "It would have been easy to walk away and inform Lauren that her heart is fine," Turakhia said. "However, I wasn’t convinced."
Turakhia decided to go one step further and conduct an electrophysiological study that is not typically used in diagnosing ARVC. He and his colleagues carefully threaded several catheters with electrodes into her heart from blood vessels in her leg to create a three-dimensional map of the electrical voltage in her heart. Then, they induced the tachycardia. Results of the study pointed to evidence of scar tissue consistent with ARVC in her right ventricle.
"Patients with a more benign form of tachycardia don’t have this kind of scarring," said Marco Perez, MD, an instructor in cardiovascular medicine at the School of Medicine and member of the Center for Inherited Cardiovascular Disease. "Although not definitive, this finding pointed to ARVC as the most likely diagnosis."
Sassoubre had a defibrillator implanted in her chest that could sense when she had ventricular tachycardia and deliver pulses of electricity to terminate the abnormal rhythm. It could even deliver a shock to resuscitate the heart in the unlikely event of cardiac arrest. She also underwent a procedure in which a catheter was used to destroy some of the problem-causing heart tissue. Since then, she has been taking medication to help suppress the abnormal rhythms.
But even after leaving the hospital, the diagnosis had a major impact on how Sassoubre would lead her life, and it would also have implications for her extended family. It was important to know for sure she had inherited ARVC, and the center offered a tool that could potentially provide that certainty: a genetic test, in which DNA is extracted from a blood sample and then analyzed using a sequencing machine. When the findings came back a couple of months later, they confirmed Turakhia’s early suspicions. "This is now proof positive," he said.
Sassoubre had a mutation of the PKP2 gene, which normally makes a protein called plakophilin-2 found in heart muscle. In her case, however, the faulty protein was not doing what it should; instead, it was causing the build-up of a fatty, scar-like tissue in the organ wall. This tissue disrupted the electrical signal controlling her heartbeat.
ARVC is thought to occur in 1 of every 2,000 to 5,000 U.S. adults, although the exact risk is unknown. It can be aggravated by exercise.
To learn more about the ramifications of the diagnosis, Sassoubre and some of her family members met with the genetic counselor, Colleen Caleshu, who joined Stanford last year with the launch of the Center for Inherited Cardiovascular Disease.